This invention relates to a fiber reinforced composite article and its manufacture. More particularly, it relates to a fiber reinforced composite article such as a composite blading member including an airfoil, the article including generally transverse or angled reinforcing members.
Components for sections of gas turbine engines, for example a fan and/or a compressor, operating at relatively lower temperatures than sections downstream of the combustion section have been made of resin matrix composites including stacked, laminated layers. Generally such primarily non-metallic composite structures, which replaced heavier predominantly metal structures, include superimposed layers, sometimes called plies, reinforced with fibers substantially in the plane of the layer. As used herein, fibers include within it meaning filaments in a variety of configurations and lay-up directions, sometimes about a core and/or with local metal reinforcement or surface shielding. For elevated temperature applications, a variety of materials are used for such fibers, including carbon, graphite, glass, metals (forms of which sometimes are called boron fibers), etc., as is well known in the art. Typical examples of such components made primarily of non-metallic composites are reported in such U.S. Pat. No. 3,892,612xe2x80x94Carlson et al. (patented Jul. 1, 1975); U.S. Pat. No. 4,022,547xe2x80x94Stanley (patented May 10, 1977); U.S. Pat. No. 5,279,892xe2x80x94Baldwin et al. (patented Jan. 18, 1994); U.S. Pat. No. 5,308,228xe2x80x94Benoit et al. (patented May 3, 1994); and U.S. Pat. No. 5,375,978xe2x80x94Evans et al. (patented Dec. 27, 1994).
As has been discussed in detail in such patents as the above-identified Evans et al. patent, such non-metallic composites in an aircraft gas turbine engine are subject to damage from ingestion into the engine and impact on components of foreign objects. Such objects can be airborne or drawn into the engine inlet. These include various types and sizes of birds as well as inanimate objects such as hailstones, sand, land ice, and runway debris. Impact damage to the airfoil of blading members, including fan and compressor blades, as well as damage to strut type members in the air stream, has been observed to cause loss of material and/or delamination of the stacked layers. Such a condition in a rotating blade can cause the engine to become unbalanced resulting in potentially severe, detrimental vibration.
The above identified and other prior art have reported various arrangements and structures to avoid such material loss and/or delamination of layers. Some arrangements, for example U.S. Pat. No. 3,834,832xe2x80x94Mallinder et al. (patented Sep. 10, 1974) and the above-identified Benoit et al. patent, include use of seams or fastening devices disposed transversely through an at least partially solidified, reinforced resin matrix that fixes reinforcing fibers in a position. Their purpose is to avoid delamination of laminated composite structures using ordinary commercial resin systems as the composite matrix. It has been observed, however, that disposition of such transverse reinforcement through a generally solidified or at least partially cured resin reinforced layer or preform of an article, with reinforcing fibers held by a resin in a fixed position, can fracture, tear or otherwise damage the fibers reinforcing the layer. Such damage can reduce the operating integrity and life of a composite article.
The present invention, in one form, provides a method for making a fiber reinforced composite article comprising a plurality of stacked layers and including additional reinforcing members disposed at an angle, for example generally transverse, to planes of the stacked layers without damage to in-plane fibers reinforcing the layers. The method comprises providing a plurality of layers of first, substantially dry, unimpregnated reinforcing fibers, herein sometimes called in-plane fibers. In a preferred form, such first reinforcing fibers generally are aligned with one another in the layers. Such layers are stacked generally upon one another into a preform of a stack of layers. While in the dry, unimpregnated condition, a plurality of spaced apart additional or second reinforcing members is inserted into the preform at an angle to the stack of the layers. One preferred example is an angle generally transverse to such stack of layers of the preform. Then the preform is impregnated with a matrix about the first reinforcing fibers and the second reinforcing members.
In another form, the present invention provides a fiber reinforced composite article. Such article includes a plurality of stacked layers of first reinforcing fibers and a plurality of second reinforcing members disposed into the article at an angle to the stack of layers. The second reinforcing members are disposed beside or adjacent to the first reinforcing fibers. A substantially solid matrix is disposed about the first reinforcing fibers and second reinforcing members.